diff --git a/lib/Service/Proposal/ProposalService.php b/lib/Service/Proposal/ProposalService.php
index 06bbf8e569..f4b49beb48 100644
--- a/lib/Service/Proposal/ProposalService.php
+++ b/lib/Service/Proposal/ProposalService.php
@@ -375,6 +375,7 @@ public function convertProposal(IUser $user, int $proposalId, int $dateId, array
 				$vObject->serialize()
 			);
 		}
+		$this->applyCalendarBlockersParticipant($user, $proposal, 'M', $vObject);
 
 		// destroy the proposal entry
 		$this->proposalVoteMapper->deleteByProposalId($user->getUID(), $proposal->getId());
@@ -633,7 +634,7 @@ private function syncCalendarBlockers(IUser $user, ProposalObject $proposal, str
 		$vObject = $this->constructCalendarBlocker($user, $proposal);
 
 		$this->applyCalendarBlockersOrganizer($user, $userCalendarUri, $userEventUri, $vObject);
-		$this->applyCalendarBlockersParticipant($user, $proposal, $reason, $userCalendarUri, $userEventUri, $vObject);
+		$this->applyCalendarBlockersParticipant($user, $proposal, $reason, $vObject);
 
 	}
 
@@ -720,7 +721,7 @@ private function deleteCalendarBlockersOrganizer(IUser $user, string $calendarUr
 	/**
 	 *  Create or update calendar blocker event(s) for participant(s)
 	 */
-	private function applyCalendarBlockersParticipant(IUser $user, ProposalObject $proposal, string $reason, string $calendarUri, ?string $eventUri, VCalendar $vObject): void {
+	private function applyCalendarBlockersParticipant(IUser $user, ProposalObject $proposal, string $reason, VCalendar $vObject): void {
 		// if the calendar manager does not have a handleIMip method, we cannot generate iTip messages
 		if (!method_exists($this->calendarManager, 'handleIMip')) {
 			return;
diff --git a/tests/php/unit/Service/Proposal/ProposalServiceTest.php b/tests/php/unit/Service/Proposal/ProposalServiceTest.php
index e36add0754..c62d245a8b 100644
--- a/tests/php/unit/Service/Proposal/ProposalServiceTest.php
+++ b/tests/php/unit/Service/Proposal/ProposalServiceTest.php
@@ -580,6 +580,16 @@ public function testConvertProposalSuccess(): void {
 			->method('deleteById')
 			->with('testuser', 1);
 
+		// the internal participant must be looked up and notified of the finalised event via iTIP
+		$participantUser = $this->createMock(IUser::class);
+		$participantUser->method('getUID')->willReturn('alice');
+		$this->userManager->expects($this->once())
+			->method('getByEmail')
+			->with('alice@example.com')
+			->willReturn([$participantUser]);
+		$this->calendarManager->expects($this->once())
+			->method('handleIMip');
+
 		// test and assertions
 		$this->service->convertProposal($this->user, 1, 10, ['attendancePreset' => true]);
 		$this->addToAssertionCount(1); // If we reached this point, the test is successfully completed